The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Active fuel management (AFM) or cylinder deactivation may be used to improve fuel economy in vehicles. Cylinder deactivation includes deactivating one or more cylinders of an engine during low load and cruising conditions to reduce pumping losses. When a cylinder is deactivated using AFM valve control strategies, the exhaust valve is deactivated before the intake valve. A burned charge of air that is above atmospheric pressure is trapped in the cylinder. The trapped burned charge remains trapped in the cylinder providing a gas spring effect on the pistons.
Engine start-stop operation may be used to improve fuel economy in vehicles. During periods when an engine would normally be idling, control cuts fueling to the engine causing the engine to stop. When the system senses that the driver is about to request the vehicle to accelerate, control restarts the engine.